The present invention is directed to an inflatable passenger restraint system, and more particularly to an airbag inflation apparatus and method for regulating inflation in response to occupant parameters.
An inflatable passenger restraint system, such as an airbag, deploys when sensors in a vehicle detect conditions of an impending crash. The airbag is designed to protect vehicle occupants from impact with parts of the vehicle, such as the steering wheel, dashboard, and windshield. In some cases, side airbags protect vehicle occupants from impact with the sides of the interior of the vehicle.
However, airbags often injure rather than protect vehicle occupants. For instance, airbags may inflate too rapidly and forcefully resulting in bruises, broken bones, and even death, especially in smaller adults and children. In fact, automobile manufacturers recommend that young children ride in the backseat of a vehicle away from an airbag to avoid injury and possibly death from an airbag in the event of a crash. To prevent such injuries and deaths from airbags, manufacturers have sought to control airbag inflation using valves and other means.
Mechanically controlled, pyrotechnically controlled, electronically controlled, and pressure assist valves are currently utilized in controlled inflation airbag systems. However, mechanically and pyrotechnically controlled valves are costly and complex. Electronically controlled valves have a slow response time and often require mechanical springs that further increase response time and power required. Pressure assist valves minimize time required to completely open a valve, however, they restrict the ability to rapidly close or otherwise adjust the position of the valve after opening.
Other means of regulating airbag inflation include multiple inflation containers and multiple level inflators. However, multiple level inflators are expensive to manufacture due to the need to integrate two or more stored energy devices into one inflator. Also, the entire inflator must be replaced if one stored energy device is activated.
Numerous U.S. patents disclose airbag systems utilizing valves to regulate the flow of inflation fluid into the airbag. U.S. Pat. No. 5,161,776 discloses a solenoid valve assembly that is well suited for use in motor vehicle air bag assemblies. U.S. Pat. No. 5,582,425 teaches an airbag inflation system comprising a valve mechanism including two valves. One valve opens to initiate gas flow and a second valve controls gas flow by gradually increasing the flow passage area with the movement of a movable valve member. U.S. Pat. No. 5,927,753 teaches an airbag system with a valve that is actuable to regulate flow of inflation fluid through the valve so as to vary rates at which the inflation fluid pressure increases in the protection device. The valve may be a solenoid valve. U.S. Pat. No. 5,947,514 discloses an airbag system with controlled airbag inflation through the use of a throttling valve module including pintle valves, spool valves, and other electrically controlled valves. U.S. Pat. No. 6,076,852 teaches an airbag inflation apparatus which regulates the flow of inflation fluid using a solenoid valve to control outflow area.
U.S. Pat. No. 5,707,078 teaches an air bag module with adjustable cushion inflation provided by a valve member. The valve member is moved in one direction to simultaneously increase the size of the inflation outlet into the airbag while decreasing the size of the vent outlet and is moved in another direction to simultaneously decrease the size of the inflation outlet into the airbag while increasing the size of the vent outlet. The valve member is positioned by a control unit which receives input from various sensors within the vehicle regarding such factors as ambient temperature, occupant position, occupant weight, seat belt usage, etc to produce an optimum cushion inflation based upon these factors. An electromagnet, solenoid, or other device can be used to move the valve member, however, the valve member does not incorporate a magnetic fluid. This patent differs from the present invention as the valve described in the present invention does not contain a valve member that physically moves and controls the size of the inflation outlet into the airbag, rather only the particles within the magnetic fluid change position to control the gas inflation rate into the airbag.
U.S. Pat. No. 6,036,226 discloses a “smart” airbag inflator with a piston for regeneratively pumping liquid propellant from a reservoir into a combustion chamber for ignition and combustion to generate airbag inflation gases. A magneto-rheological fluid fills a damping chamber in the piston and an electromagnet varies a magnetic field exerted on the magneto-rheological fluid. Thus, the damping force of the piston may be regulated and the damping force controls the rate of liquid propellant combustion and inflation rate of the airbag. While this patent is directed to controlling the rate of liquid propellant combustion to control the inflation rate of the airbag, the present invention controls the rate and amount of combustion gas passing between the reaction chamber and the airbag. Also, in the present invention, the rate of liquid propellant combustion always remains the same.
U.S. Pat. No. 6,039,347 discloses another airbag inflator with a pair of telescoping pistons in which liquid propellant is regneratively pumped from a reservoir into a combustion chamber for ignition and combustion to generate airbag inflation gases. Pressurization of the combustion chamber causes one piston to pressurize a hydraulic fluid chamber which causes the second piston to pressurize the liquid propellant reservoir. Again, a damping fluid such as a magneto-rheological fluid in a damping chamber of the second piston controls the rate of airbag inflation gas generation. While this patent is directed to controlling the rate of airbag inflation gas generation, the present invention controls the rate and amount of combustion gas passing between the reaction chamber and the airbag. In the present invention, the rate of airbag inflation gas generation always remains the same.
Valves employing magnetorheological (MR) fluids to control gas flow are well known in the art. Magnetorheological fluids are magnetic field responsive fluids containing magnetizable particles coated with a surfactant and dispersed in a carrier liquid. These fluids typically have been used in devices, such as dampers, shock absorbers, seals, valves and the like to provide varying stress levels controlled by an external magnetic field. The variable stress is created by magnetic coupling of the particles in the form of chains or bent wall-like structures upon interaction with an external magnetic field. As to the composition, these fluids are typically made of micron-sized particles dispersed in an engineering medium, such as hydraulic oil, mineral oil, or water, or the like.
U.S. Pat. No. 6,044,866 teaches a gas flow valve comprising at least one gas inlet, at least one gas outlet, a magnetic fluid arranged in the gas flow path such that the gas must pass trough the magnetic fluid, and a means for application of a magnetic field such as a permanent magnet or an electromagnet. The gas flow valve utilizes the change in viscosity of the magnetic fluid due to the application of a magnetic field to control the gas flow through the valve. The valve is capable of permitting partial gas flow in addition to no gas flow and full gas flow so that the gas volume flowing through the valve in accordance with the invention can be continuously adjusted. However, the patent does not suggest any applications of the valve and it is not used in a controlled airbag inflation system. Further, the patent only generally discloses that any type of magnetic fluid may be used in the valve, while in the present invention it is necessary to carefully design and produce the magnetic fluid used in the valve located between the reaction chamber and the airbag. The properties of the magnetic fluid such as viscosity and yield stress must be extremely controllable upon the application of varying degrees of a magnetic field in order to protect the passengers in the vehicle. The response time of the magnetic fluid must also be extremely fast in order to inflate the airbag during a collision.
U.S. Pat. No. 6,186,176 discloses a method and system for controlling the flow of a gaseous medium through a fluid using an electrorheologic fluid, a means of guiding the gaseous medium through the electrorheologic fluid, and a means for applying an electric field at least partially in the area of the electrorheologic fluid. The viscosity of the electrorheologic fluid is controlled by the application of the electric field thereby controlling the flow of the gaseous medium through the electrorheological fluid. The means of guiding the gaseous medium through the fluid can be a shaped container. Preferably, the gaseous medium is air. The patent also suggests that the system may be used as a control valve or an overpressure valve.
There is thus a need for an inflatable passenger restraint system with controlled airbag inflation. In the present invention, a valve employing a magnetorheological fluid to control gas flow is applied to an inflatable passenger restraint system. More specifically, the present invention provides an alternative valve means utilizing the properties of a magnetic fluid to control the inflation rate of an airbag.